Second opinion on gas system.

Loganator

Loganator

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Peoples republic of Ontario
Hello. Need a second opinion on my gas system.

I took my 14.5 inch carbine build with h2 buffer which ran like a top, and added a 20 inch barrel with rifle length gas system to it with the same h2 buffer which does not cycle.

Lower pressure on longer barrels correct? I am thinking lighter buffer and I will be good. Anyone second that motion.

Thanks in advance.
 
Yes to less pressure but hard to diagnose an under pressure issue with just "does not cycle". Extracts? Ejects far or close? Picks up new round? Sticks on feed ramp? Doesn't go fully in battery?
 
Loganator said:
Hello. Need a second opinion on my gas system.

I took my 14.5 inch carbine build with h2 buffer which ran like a top, and added a 20 inch barrel with rifle length gas system to it with the same h2 buffer which does not cycle.

Lower pressure on longer barrels correct? I am thinking lighter buffer and I will be good. Anyone second that motion.

Thanks in advance.
Click to expand...

Use a regular carbine buffer with a rifle gas systems as the H series of weights are reserved for carbine gas length sytems to dampen the violent cycling. No need for the longer barrels.
 
I think your problem might be bigger than the wrong buffer weight. Definitely go with a regular buffer if you don't want to get a rifle extension, but I would be looking at a loose or missaligned gas block? Missaligned gas tube? Your gas key should be fine if it was working on the 14.5".
 
If you know anyone else with an AR that has a regular carbine weight buffer ask to borrow it and see if it fixes the problem. Sounds like it's almost cycling the bolt far enough but not quite. I would definitely check for a misaligned gas block though as it should still cycle with an H buffer.
Some gas blocks have the hole spacing set for having the front ring that supports the non free floated forend so you may need to leave a small gap between the front of the gas block saddle and the back of the gas block to get a smooth flow of gas into the gas block. Removing it and measuring it with some calipers will tell you if that is your problem.
Did you change anything else or just the barrel, gas block, and gas tube?
Standard carbine buffers are cheap so even if it isn't the problem you won't be out much cash and there's nothing wrong with having some spare parts for your next build, I think I saw some for sale on the EE the other day.
 
Funny how a 20inch with the rifle buffer 5oz cycle but not a 4.6oz h2 buffer. Maybe the spring is weaker in a rifle tube
 
If you can't find anyone with a carbine buffer, as a temporary test, you could always just remove one or two of the tungsten weights from yours and try it like that. If it cycles, get a carbine buffer. If not, your gas port may be too small.
 
Loganator said:
Thanks. Checking for alignment was the first thing i did. Will double check again
Click to expand...

Check alignment not only rotationally but also forward/backward, like I said earlier it may a mismatch between your barrel and the gas block.
A 20 inch barrel likely has the gas block saddle cut for use with a non free floated forend and a gas block with a front sight and if your gas block is for a free float (low profile gas block without sight) it may need to be spaced forward towards the muzzle slightly to line up the ports. A buddy of mine ran into this recently with one of his builds.
 
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